It is well known in the art of photographic science to add dyes to the structure of a photographic element in such a way as to absorb deleterious light. The dye can be located in several positions including: between the exposure source and the photosensitive emulsion; between the photosensitive emulsion and the support; and on the opposite side of the support to inhibit halation. Specific applications are illustrated, for example, in Research Disclosure, No. 308, December 1989, Item 19.
Antihalation is particularly important when a film is exposed with a laser such as in the use of long wavelength laser films for medical imaging. The high intensity of long wavelength light (i.e. near-infrared) emitted by the laser is difficult to filter completely. If high levels of a dye are used it is typically difficult to remove the dye during processing and the result is a coloration, or dye stain, which is undesirable.
The development of the gallium-arsenic semiconductor laser, or diode laser, is expected to extend the use of lasers for medical imaging into the wavelength range of 780-830 nm. This application requires a film which is sensitive in this wavelength range and has an antihalation layer which absorbs in this region and is stable with time. Provided herein is a novel class of dyes which absorb throughout the near-infrared region and are well suited for use as an antihalation dye.